Stress concentration study in steel elastic element of load cell
Abstract This paper study the stress concentration in one of the important force measuring device (load cell ). The elastic element of load cell have many type but in this paper We will be interested in studying one of the most common types of load cell, we will study the stress concentration in one popular spring element design is the binocular conguration, which is a beam with two holes and a web of beam material removed, as shown in Figure 1. There for we will determine the stress concentration in tow design of binocular load cell type using ansys simulation program
Introduction ost industrial measurements of force are made with strain gauge load cell. !t utili"es strain gauges bonded to steel body to give an electrical output proportional to applied force. #i$erent types of load cells are beam type, %&% type, cantilever type etc. These are used for tension measurements, weighing, industrial automation and research applications, etc. ost commonly, shape optimi"ation is the process of changing the physical dimensions of a structural part to reduce weight while staying within design constraints, usually ma'imum stress or deection shape optimi"ation can include, but is not limited to optimi"ing items such as llet radius, hole diameter, and width or height of a part. sually, shape optimi"ation is performed on solid models, although there are many applications for surface models (shells) (*+&& -.1, Theory eference, #esign /ptimi"ation). &hape optimi"ation lin0s nite element analysis and parametric geometric construction to ma0e it possible to e'plore di$erent design options. !t involves varying certain design parameters (e.g. dimensions) while observing other criteria (e.g. ma'imum allowable stress) until the best and most economical design is found. While nite element analysis is primarily a tool used to verify a design, it can also be the rst step toward improving a design. * rstpass nite element analysis might show that stresses and other design responses are well below a prescribed limit, which indicates that it is safe to ma0e some design changes. For e'ample, you may modify certain dimensions to reduce the amount of material needed.
Fig (1) the two model of binocular load cell
Model Verication: The two model made from steel with young modules e2ual to (344e5) and all dimensions of the tow to model are show in gure (3)
Finite Element Method Finite 6lement
*nalysis
is an engineering techni2ue utili"ed to behavior the structures for e'act e'ist. While it historical s in structural nite element is now applied variety of ng areas,
analysis is that simulate of comple' which no solutions has its beginning analysis, analysis to a wide engineeri
uid ow, transfer, and .gnetic
including heat electroma
Fig 7 Block diagram for simulation process
The results and analysis:
Fig. 4 Tow model of ‘binocular’ Type Load Cell 3! "odel
Fig. # "es$ed "odel
Fig. %
!eformed & 'nreformed s$ape
Fig. ( )tress distribution
First model
&econd model
8oad(9+)
a'. stress (pa)
a'. strain
1 14 144
:.;57e5 :.;57
4.4<1=; 4.73;4< <.1=;7
a'. deformation (mm) 4.<137 <.137; <1.37;
a'. strain
a'. stress(pa)
4.4=377 4.=377 =.377
1.;44-e14 1.;44-e11 1.;44-e13
a'. deformation (mm) 1.43<< 14.3<< 143.<<
Table *+, t$e results
*s we see that the stress , strain and deformation in the second model is great than the rst model that mean the second model has a great sensitivity due to change in load rather than the rst .
Conclusion: 8oad cell design is challenging due to the comple' geometry of spring elements. ansys solid models are useful for predicting strain in these designs, for locating strain gage mounting positions and especially for optimi"ing ma'imum strain for the desired load range. as we see in the result of analysis of to model if we need high accuracy in measurement of the force we most use the second model but the problem in this model that the stress construction is very high for that we can%t use this model for high force . in the other hand if we need to measurement high force we can use the rst module but we will get error in measured the load more than in the rst one due to di$erences in strain of both models
Reference : >ishay icroeasurements ?odel @7 &train !ndicator *nd ecorderA !nstruction anual.<, easurements Broup, aleigh, +C (344;).
*hsan, . ., @rachurDa, @., *li, *. . ., and amun, . *. E., ?#etermination of e$ect of elliptic notches and grooves on stress concentration factors on notched bar in tension and grooved shaft under torsionA, ournal of +aval *rchitecture and arine 6ngineering, >ol.14 !ssue 1, 3417. *. 9amble >iDay and @. +. Bore G se of F6 and photo elasticity for shape optimi"ation of & type load cell G Indian Journal of Science and Technology
*+&& -.1, Theory eference, #esign /ptimi"ation
