So for checking purpose we need the loading frame loading arrangement and sensing and data acquisition system. because of suitability so that it can be established any where generally we make it self straining that means it will neutralize the reactions of applied load by itself in other words no other load transfers to ground except its self weight . And it is also necessary to characterize and check it that it will fulfill all criteria as per its serviceability and defined codal provisions or not. So here we will perform some experiments to characterize our loading frame and will make software model to analyze it with finite element analysis method. .
In any structure or structural element before application in actual field there is some testing should have to perform so that to check its reliability and serviceability. So in characterization process we have to set its limitation either they ae structural or geometrical. At some extent, in beginning of service life of any structure main aim of SHM is also that to characterize the limiting values only. Latter it defins rest of life and current performance of structure.
The Structural health monitoring can be defined as non-destructive in-situ structural evaluation method in which several types of sensors and actuators are attached or embedded in structure. Structural Health Monitoring (SHM) aims to give, at every moment during the life of a structure, a diagnosis of the “state” of the constituent materials, of the different parts, and of the full assembly of these parts constituting the structure as a whole. The state of the structure must remain in the domain specified in the design, although this can be altered by normal aging due to usage, by the action of the environment, and by accidental events.
And the rest part is Prognosis in which the prediction of residual life of the structure is to be done. Due to time-dimension of monitoring, which makes it possible to consider the full history database of the structure, and with the help of Usage Monitoring, it can be able to provide a prognosis (evolution of damage, residual life, etc.).
In structural health monitoring damage is defined as changes to the material and/or mechanical properties of a structure, including changes to the boundary conditions, which adversely affect the structural performance. These sensors collect data which is analyzed and stored for future analysis and reference that can be used for safety, integrity, strength or performance.
1.2Components of SHM
• The structure on which the SHM system will be placed.
• Sensors and Actuators
• Acquisition system
• Communication of information
• Intelligent processing and analyzing of data
• Storage of processed data
• Damage modeling and damage detection algorithms
• Retrieval of information as required
• Layout of structural health monitoring
Fig.1.1 Layout of structural health monitoring
TABLE 1.1 Categories of SHM
Static Field Testing:
Behavior tests Diagnostic test Proof tests
Dynamic Field Testing:
Stress history tests
Ambient vibration tests
Dyn. Load Allowance (DLA) tests Pullback (anchored cables) tests
Tests to determine changes in structure
• Advantages of SHM
Increased understanding g of in‐situ structural behavior
Early damage detection
Assurances of structural strength and serviceability
Decreased down time for inspection and repair
Development of rational maintenance / management strategies
Increased effectiveness in allocation of scarce resources Enables and encourages use of new and innovative materials
• Levels of SHM
LEVEL I: This basic level SHM system is capable of detecting damage in a structure, but cannot provide any information on the nature, location or severity of the damage .it cannot assess the safety of the structure.
LEVEL II: Slightly more sophisticated than level 1 SHM system level II system can detect presence of damage and can also provide information about its location.
LEVEL III: In this level we can locate pin point location and of damage and its severity .
LEVEL IV: It is the most sophisticated system of SHM and provide detailed information about presence, location and severity of damage and in some extent it can also provide information about the life of the structure.
1.3 What is loading frame
A high stiffness support structure against which the test forces can react. The load frame comprises a base beam, two columns, and a moving crosshead. It is a self straining structure that means no other load is transfers to ground except its self weight.
Fig.1.2 loading frame
• Types of loading frame
According to axis of loading
Vertical loading frame
Fig.1.3 Vertical loading frame
Horizontal loading frame
Fig.1.4 Horizontal loading frame
(b) Other types
Straight Sided four column Type
Straight Sided box Type
Straight Sided Column/C-Frame Type,
• Significance of loading frame
The test-loading frame can be utilized to test the behavior and load-carrying capacity of both full-size structures as well as separate structural member.
This equipment is best suited for producing static and repeated loadings
1.4 Objectives of the study
• Characterization of loading frame
• to monitor health of loading frame.
• . vertical stiffness
• . displacements under characteristics load etc
• And comparative study of the general manual results with experimental results.
Outline of project
• Is to study various aspects of structural health monitoring and part of instrumentation involved in it.
• Experimental procedure and methodology.
• Describes experimental investigation.
• Description of strain gauges and its types.
• Cooperative study of experimental and theoretical results.
Scope of the future work
To achieve the above objective, to the scope of this work for the project generally involves the following.
• To verify the loading frame geometrically by performing flatness test and parallelism tests.
• To verify structural performance of frame using strain gauges LVDT’s, data logger and load cell as instrumentation part and hydraulic jack spacers as mechanical part.
• To apply the tests more times to verify reliability of our instrumentation system.
• To make completive study of results of theoretical and experimental calculation and prediction about health of frame.
I.C. Medland , (1966).
Collapse load of steel frame works allowing for the effect of strain hardening
Concerned an investigation of the behavior of structures composed of the high yield-stress steel to B.S. 968. Moreover, it concern about the applicability of the plastic theory to the design of such type of framed structures. In this investigation, he had conducted a number of bending tests on simply supported beams of having I-sections in the new steel to check the applicability of the previous theories to the estimation of the strain-hardening characteristic of such beams. He had found that the rigid-plastic-strain-hardening (r.p.s.h.) and rigid-plastic-rigid (r.p.r.1 theories both gave good estimates of the strain-hardening characteristic of high tensile steel beams and that the basic r.p.r. theory could be used as a suitable basis for a design method.
Computer aided design of hydraulic press by and P.D.Murarka (1988)
The study was concerned about computer aided design of hydraulic press in which they used finite element model to analyze the press structure and it has been used in making a comparative study of the behavior of the structure. The factors considered are fillet, edge cutting, provision of openings, change in position of stiffeners and eccentric loading. On the basis of this investigation, certain significant guidelines have been obtained for the design of press frames that are..
(i) Clearance between sliding members to be kept to a minimum, according accuracy expected of the machine tool;
(ii) Proper alignment of different elements, particularly sliding ones should be ensured.
Dr. Mohamad M. Salehet.al, ( 1992)
Design study of heavy duty hydraulic machine using FEM technique,
This thesis describes the systematic procedure for investigating the performance and the design analysis of the welded structure of a 150-tonne hydraulic press machine. This machine was designed without any measurement or variable hydraulic system. The investigation discusses the theoretical and experimental model of the machine to establish the accurately optimal design analysis and further development of the present machine at minimum time and lower cost. The applicability of the existing PC based FE package, as a computer aided design tool, was also investigated. The theoretical model takes into account both conventional analytical formula and numerical technique, using Finite Element Analysis. The conventional model is based on the simple bending theory using the total strain energy principle for 2D beams. The LUSAS Finite Element software system is used as a tool to establish the theoretically predicted numerical model. This model has been discussed with different factors. The factors considered are: the boundary condition; the mesh density and the type of the element being used. The experimental model consist of load cells strain gages and L.V.D.T. and A comparison has been made between the experimental and theoretically predicted results.
L.A. Bisby 2004
An Introduction to structural health monitoring, L.A. Bisby 2004
Concerned about the introduction to structural health monitoring and its various aspects like its components, classification, levels, methods of computation etc.
also gives a brief description of sensors and actuators and there types with some example of bridge structure.
Charles R. Farrar et.al,(2006)
An Introduction to structural health monitoring,
The study is concerned about an introductory part about SHM that The process of implementing a damage identification strategy for aerospace, civil and mechanical engineering infrastructure is referred to as structural health monitoring (SHM). damage is defined as changes to the material and/or geometric properties of these systems, including changes to the boundary conditions and system connectivity, which adversely affect the system’s performance. it also concerned about wide variety of highly effective local Non-destructive evaluation tools are available for such monitoring and also tells about motivation for SHM technology development, feature extraction and information condensation, Operational evaluation and Challenges for SHM.
Mohammad Osman et al (2011)
Finite element analysis of beam-column joints in steel frames under cyclic loading.
This study is concerned to develop simple and accurate three-dimensional (3D) finite
element model (FE) capable of predicting the actual behavior of beam-to-column joints in steel frames subjected to lateral loads. The software package ANSYS is used to model the joint. The bolted extended-end-plate connection was chosen as an important type of beam–column joints. The extended-end-plate connection is chosen for its complexity in the analysis and behavior due to the number of connection components and their inheritable non-linear behavior. Two experimental tests in the literature were chosen to verify the finite element model. The results of both the experimental and the proposed finite element were compared. One of these tests was monotonically loaded, whereas the second was cyclically loaded. The finite element model is improved to enhance the defects of the finite element model used. These defects are; the long time need for the analysis and the inability of the contact element type to follow the behavior of moment–rotation curve under cyclic loading. As a contact element, the surface-to-surface element is used instead of node-to-node element to enhance the model. The FE results show good correlation with the experimental one. An attempt to improve a new technique for modeling bolts is conducted. And Concluded that FE results and the experimental results are compared to examine the validity and the predictability of the proposed model. The FE results have good agreement with the experimental one at different stages of loading. The FE model can provide a variety of results at any location within the model. A viewing of the full fields of stresses and strains are possible in the FE model. This provides a great advantage in monitoring the components of the connection.and shown that modeling a beam-to-column connection loaded cyclically is expensive and time consuming in both building and solving the model. So, there is a great need to model the connection more simply and at the same time with an acceptable accuracy. and gave a proposal for a new technique of modeling bolts is presented. The proposal is to model the bolts as a mixing of shell elements (for head and nut) and link elements (for shank). This technique for modeling of bolts, called shell bolt, was examined and compared to other methods for modeling of bolts and was found to be accurate. Also, it needs less time of solution and less storage volume comparing with other techniques for modeling the bolts.
Philip Rinn et al (2012)
Stochastic method for in situ damage analysis,
study is concerned about physics of stochastic processes we present a new approach for structural health monitoring. this new method allows for an in-situ analysis of the elastic features of a mechanical structure even for realistic excitations with correlated noise as it appears in real world situations. In particular an experimental set-up of undamaged and damaged beam structures was exposed to a noisy excitation under turbulent wind conditions. The method of reconstructing stochastic equations from measured data has been extended to realistic noisy excitations like those given here. In our analysis the deterministic part is separated from the stochastic dynamics of the system and we show that the slope of the deterministic part, which is linked to mechanical features of the material, changes sensitively with increasing damage. The results are more significant than corresponding changes in eigen frequencies, as commonly used for structural health monitoring. Commonly detection systems use fast Fourier transformation (FFT) to extract system features and to determine the condition of the system from changes in the eigen frequencies. One drawback of this approach is that noisy excitation of the structure broadens the peaks of the frequency spectrum and thus makes it harder to detect changes reliably.
Yasin Kisioglu et.al,(2013)
Hydraulic press design under different loading conditions using finite element analysis, Mehmet Aydin and Yasin Kisioglu (2013)
this study, a suitable hydraulic press having four-column is designed and the stress distribution is calculated using both analytical and finite element methods under different loading conditions. Three different loading types, axial, eccentric and oblique, are considered in design process. Six different types of standard sections having the same cross-sectional area are used for the press columns. Three different models for the press head are designed to hold the hydraulic cylinder. Therefore, eighteen different design combinations for a hydraulic press are modeled under three different loading conditions. Their stress distributions are calculated using a computer-aided finite element analysis (FEA) tool and analytical formulas and the obtained results are compared. Two different types of finite elements, shell and beam, are used for the modeling processes. Based on the obtained results, the best model for the hydraulic press considering the head and body types is defined. and recommended that T type head and hollow circular or I-sectioned column is the best design consideration.
Martin Zahalka et.al, (2013)
Modal analysis of hydraulic press frames for open die forging,
the study discuss the dynamic behavior of the forging machines is necessary to explore due to the increasing of speeds on large forging hydraulic presses for open die forging. The study describes the modal analysis of two selected presses, which represent the most common designs of hydraulic presses for forging. The first press is with double-column frame CKV 50 with the force 50MN and the second one is with four-column frame CKV 170 with the force 170 MN. Further are described the simulations of oscillation, which was excited by time-dependent work force. Results of analysis are compared with measurement in the real operation. w and concluded that we can get higher second moment of area with the same area of cross section by changing of shape only.
Santosh kumar S.Malipatil et al (2014)
Analysis and structural optimization of 5 ton H-frame hydraulic press,
Discussed about Using the optimum resources possible in designing the hydraulic presses frame can effect reduction in the cost of the hydraulic presses. By optimizing the weight of material utilized for building the structure. An attempt has been made in this direction to reduce the volume of material. So here we consider an industrial application project consisting of mass minimization of H-frame type hydraulic press. This press has to compensate the forces acting on the working plates and has to fulfill certain critical constraints. ANSYS has been used for this analysis the main aim is to reduce the cost of the Hydraulic presses without compromising on the quality of the output. With regarding to design specification, stress distribution, deflection, and cost, are focused on optimized design. The methodology followed in this work is comparison of stresses induced in machine for different thickness used for construction of frame and column of the H-frame type hydraulic press. In this project it has been compared original design of H frame type hydraulic press with design that have been optimized by using software tool (ANSYS) .
Since lot of work has been done on SHM of steel frame for both static condition the type of testing methods from analog to digital .
Further work has been done on structural analysis and optimization of loading frame and hydraulic presses we plant to replicate that for our loading frame.
Because there are so many difficulties in analogue signals about collection and retrieval of result data. So we are performing such the experiment which gives us results in digital form. Which needs an electronic data acquisition system which also enable to store the data which can be retrieved when required that’s why we have to involve some electronics Instruments and circuits which are as follows
Multi-channel Digital Automatic Data Loggers for Strain measurement.
Wheat stone bridge
Load Cells & Digital Load Indicators
3.2Multi-channel Data Loggers
It’s a major part of data acquisition system as name define its work itself it logs the data in it in its own units or we can also define them. In some cases it also works as an actuator which means it gives excitation or input to the sensors but which haven’t such excitation system in that cases we have to involve external excitation system or external controlled supply like some battery or other one. In our case we are using a sixteen channel data logger names DT-85 no. of channels define that how many sensors we can attach and read the values. So in our case we can read 16 sensors at one time instant. There is also such type of arrangement is available by which we can expand the no of channels with the help of channel expansion module up to 10 channels. It is also preferred as an actuator for some small range of excitation from 300 mille volt to 3 volt. In this case it receives the signals in certain fix time interval vary from 1 second to 30 seconds. We can also set it in a triggering system by which we can control the frequency of data collection with the help of a small button. Its having some memory in which it can store data up to a certain limit we can retrieve in the system in excel sheet or we can also retrieve it in some other storage device with the help of USB port. Data loggers are available in different frequency range small frequency data loggers are static loading cases.
Fig.3.1 Data logger
For experiment dynamic loading high frequency data loggers are required. Our data logger is of small frequency range so we using it for our case.
Again name suggesting instruments or can say transducer used for strain measurements is called strain Gauges over a free surface of any structure. They follow different principals according to their types. That means there are different types of strain gauge are available according there range least count type of measurement and scope which are as follows.
Mechanical strain gauges
Acoustical strain gauges
Optical strain gauges
Pneumatic strain gauges
Electrical strain gauge
Mechanical strain gauges
These are involves with mechanical arrangements in its working principal consist of two jaws clamped with the surface or structural on which strain is desired by means of spring or some clamping arrangements at certain specific distance which is called gauge length. So when specimen or component was loaded it get elongated so the jaw clamped with component is also get displaced from its original position. And this displacement is amplified and by some mechanical arrangement and visualized on the proving ring or some dial meter. Due to its working principal in some extent it was also called extensometer. These are also having so many types are as follows.
• Berry’s strain gauge
• Huggenbeger extensometer
• Johnsson extensometer
Fig.3.2 Berry’s strain gauge
Acoustical Strain Gauge
Its working principal is based on the propagation or traveling of wave. Which mean when bonded wire is stressed or elongated its natural frequency get altered or differs from its original values so we have to amplify this change in terms strain developed. These types of gauges are highly accurate in nature.
Optical strain gauges
As the name suggests it is based on the principal of optics. In this type of gauge the pivot jaw containing a mirror and the other jaw o edge is clamped with surface of component on which strain is desired. So when the component is stressed or elongated the pivoted edge which is carrying mirror got tilt and that ‘s why mirror will also got tilt and the reflection of the illuminated scale is visible on this mirror which can be read with the help of telescope. There are two types of optical strain gauge s are known named as follows.
• Marten’s optical strain gauge
• Tuckerman optical strain gauge
Fig.3.3 Marten’s optical strain gauge
Pneumatic strain gauges
The working principal of these type of gauges are based on relative study of discharge of air between two orifice in which one is fixed and other is variable. Sensitivity of these type gauges are 100000 times of other types. And can be used for both static and dynamic condition.
Fig.3.4 Pneumatic strain gauges
Electrical strain gauge
It also having three types but hear we are using resistance so we will explain about resistance type only. Others name are as follows.
• Inductance type
• Capacitance type
• Resistance type
These strain gauges works on the principal that they amplify the mechanical deformation or change of structural component in electrical output. It may be of any type in impedance or resistance. It consists of a conductor circuit in its structure attached with component. So when conductor is starched or compressed it results change in resistance of conductor because cross sectional area of conductor got change either increased or decreased. Change in resistance per unit strain is known as gauge factor which indicates about the sensitivity of strain gauge. There different types of strain gauges are available are as follows.
• Un-bonded wire strain gauge
• Bonded wire strain gauge
• Foil strain gauge
• Weldable strain gauge
Un-bonded wire strain gauge
This type of strain gauge gives electrical signal output of relative displacement of one body to another body. It consists of a stationary frame and a movable platform and pins made of insulated material are in those pins loops of wire are wounded which are in pretension. So when component is elongated or contracted the relative movement between frame and platform will occurs and tension in loops get alters after that this is connected with for arm wheat stone bridge for the accuracy purpose. These type of strain gauges are also used for the measurement of force pressure acceleration etc.
Fig.3.5 Un-bonded wire strain gauge
Bonded wire strain gauge
it consists of wire bonded around a core which is sandwiched between two insulating layers. Sometimes core is flattened this then this is called Flat-grid strain gauge type is also sub divided into three another types.
• Wrap-around wire strain gauge
• Flat-grid strain gauge
Fig.3.6 Bonded wire strain gauge
Weldable strain gauge
They are mainly invented due to ease in installation working principal is same as that of other resistance based strain gauges. There installation is easy. And they can work in any environment. It consists of strain sensitive material and stain component is highly insulated by compacted ceramic. Stain gauge is spot weld on structural component and when structure is stressed the stress get transmitted through weld into strain tube. These types of strain gauges also have dynamic application.
Fig.3.7 Weldable strain gauge
Foil strain gauge
This type of strain gauge consisting of a membrane of larger width as compare to its thickness and it is made up of strain sensitive material and principal is same means when structural component is strained foil also experiences strain and its resistance get changed. A suitable cementing material should also be required for bonding of strain gauge with structural component.
The strain gauge which we are using is of foil type having following specification
Resistance - 120 ohm and 350 ohm lead attached
We have also used wheat stone bridge system for better accuracy purpose.
Fig.3.8 Foil type strain gauge
3.4Wheat stone bridge
It’s an arrangement of resistances used for achieving greater accuracy in measurement. It consists of two resistances connected in series an again they connected parallel with another two resistance of same resistance value.
Fig.3.9 Wheat stone bridge
3.5Load Cells & Digital Load Indicators
As the name suggests it is an electromechanical device or equipment used to read the value of load is called load cell gives the value of load in digital format. It can be say that it’s a transducer as it converts mechanical forces into the form of electrical energy or signals .Its basic principal of working is based on the strain gauges. The internal structure or sensing system of load cell consists of a Wheatstone full bridge system of strain gauges. So when load is applied then the strain in strain gauges will increases linearly because of another principal hook’s law and because of that resistance will also increasing linearly with the deformation. There are so many different types of load cells are available according to different criteria’s as follows.
• According to construction material
• Aluminum load cell
• Tool steel load cell
• Stainless steel load cell
• According to external structure and working
• Canister type
• Single ended beam type
• Double ended beam type
• Cantilever beam type
• S-beam type
• Platform type
Hear we used a canister type of load cell having capacity of 50 ton or 500 KN shown bellow.
Fig.3.10 Load cell
3.6Displacement Transducers (LVDT)
Displacement transducer name LVDT expands and form linear variable differential transducer. Its function is to convert linear displacement caused by any mechanical mean into an electrical signal in output containing magnitude and direction. Its internal structure consists of transformer means its having two coil named primary and secondary. Primary coil wounded at mid over a hollow cylindrical and non-conductive generally made up of glass polymer. And secondary windings are wounded on top and bottom on hollow tube means on both sides of primary one. A core made up of ferromagnetic material and a its length should be a fraction of length of whole assembly containing insulator tube primary winding and secondary winding. So that when core energized primary one and move towards bottom coil flux changes and voltage, will decreases so voltage difference increases and readings are shows on display. Our LVDT’s maximum range to measure displacement is 40mm that is 20mm in positive side and another 20mm are on negative side. An image of LVDT and its indicator display is shown bellow.
Fig.3.12 DIGITAL DISPLAY of LVDT
We also require some more instruments that are not have any electronic phase
• Loading frame
• Hydraulic Jack
• Other accessories
We have given its brief introduction earlier. And our loading frame having following specifications.
Firstly sectional properties of beam-
• Depth of the section h = 600 mm
• Width of the flange bf = 210 mm
• Thickness of the flange tf = 20.8 mm
• Thickness of the web tw = 12 mm
• Radius at root r1 =20 mm
• Depth of web d = h- 2(tf + r1) = 518.4 mm
• Section Modulus Ze= 3060.4 x 103 mm3
• Plastic Modulus Zp = 3510.63 x 103 mm3
• . Weight per Meter W = 1202.71 N/m
• Capacity of frame=500 KN
Specifications of stiffeners
• ISLC 75 section
Fig.3.13 Loading frame
It’s a setup in which we can apply large mechanical loads with help of a suitable hydraulic arrangement. Consists of a pressure gauge with analog dial, piston, cylinder, oil filling and exit arrangement and a lever by which we can apply pumping force and it also have a release valve to remove or to release pressure.
The hydraulic jack we used having maximum capacity to apply load of 50 ton or 500 KN its least count is 2 KN and it also have locking arrangement for lever pump.
Fig.3.14 Hydraulic Jack
3.9 Other accessories
It consists of accessories like adhesive, spacers shielded wires, special cello tape for strain gauges, stands for LVDT, Teflon sheet, soldering iron, machine and wire, flux etc.
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