Experimental investigation on the subsurface stress distributions in specimens with different strengths after ultrasonic impact treatment

An experimental investigation is presented for the stress distributions in functionally graded plates containing a circular hole. On the basis of the authors’ previously constructed theoretical model, two kinds of graded plates made of discrete rings with increasing or decreasing Young’s modulus were designed and fabricated in virtue of multi-material 3D printing. The printed graded plates had accurate size, smooth surface, and good interface. The strains of two graded plates under uniaxial tension were measured experimentally using strain gages. The stresses were calculated within the range of linear elastic from the measured strains and compared with analytical theory. It is found that the experimental results are consistent with the theoretical results, and both of them indicate that the stress concentration around the hole reduces obviously in graded plates with radially increasing Young’s modulus, in comparison with that of perforated homogenous plates. The successful experiment in the paper provides a good basis and support for the establishment of theoretical models and promotes the in-depth development of the research field of stress concentration in functionally graded plates.

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Influence of an Inlet Oil Meniscus Geometry on Parameters of a Point Elastohydrodynamic Contact

Journal of Tribology ◽

10.1115/1.2832444 ◽

1997 ◽

Vol 119 (1) ◽

pp. 112-125

Author(s):

I. I. Kudish ◽

M. Ya. Panovko

Keyword(s):

Free Boundary ◽

Boundary Conditions ◽

Reynolds Equation ◽

Contact Region ◽

Numerical Results ◽

Contact Boundary ◽

Frictional Stress ◽

Stress Distributions ◽

Pressure Gap ◽

Subsurface Stress

In the present paper an isothermal elastohydrodynamic problem for a lightly loaded lubricated point contact of elastic bodies is formulated and studied numerically. Mathematical formulation of the problem is based on a steady nonlinear system of integrodifferential equations: Reynolds’ equation, equations of elasticity, boundary conditions for pressure, and the equilibrium condition. Nonlinearity of the problem is caused by nonlinearity of the Reynolds equation and the boundary conditions for pressure describing a free boundary. The inlet contact boundary is considered to be known and located close to the center of the contact. In order to determine the location of the free boundary (exit boundary of the contact region) the problem is formulated as a problem of complementarity by Kostreva (1984a) and Oh (1984). The dimensionless system of equations and inequalities for the elastohydrodynamic lubrication (EHL) problem is solved using the Newton-Raphson method. The inlet boundary of a contact region is considered to have a complex irregular shape (the inlet oil meniscus has some deep notches) which is taken into account while deriving the finite-difference equations. The effect of the shape and location of the inlet oil meniscus on the lubrication film thickness, pressure, gap, sliding and rolling frictional and subsurface stress distributions are considered. Some numerical results are presented for pressure, gap, frictional and subsurface stress distributions in EHL contact. These numerical results show that variations in the inlet meniscus shape and location may cause significant qualitative and quantitative changes in distributions of parameters of a lubricated contact. For instance, the maximum values of pressure may change by 20 percent, and for rolling frictional stress by 100 percent and even more.

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Force Fits and Shrinkage Fits in Crank Webs and Locomotive Driving Wheels

Proceedings of the Institution of Mechanical Engineers ◽

10.1243/pime_proc_1934_127_018_02 ◽

1934 ◽

Vol 127 (1) ◽

pp. 249-275 ◽

Cited By ~ 1

Author(s):

E. G. Coker ◽

Miss R. Levi

Keyword(s):

Experimental Investigation ◽

Stress Distribution ◽

Plane Stress ◽

Point Of View ◽

Experimental Point ◽

Engineering Practice ◽

Stress Distributions ◽

Balance Weight ◽

Driving Wheel ◽

General Method

This experimental investigation relates to a general method of measuring stress distribution when force fits and shrinkage fits of the plane stress type are employed in engineering practice. Important cases occur in the webs of built-up crankshafts for locomotives and Diesel engines. When the latter are of high power and short stroke, so that crankshaft and crankpins are large and relatively close together, the initial constructional stresses are shown to attain high values. More complicated cases, from an experimental point of view, occur in the driving wheels of locomotives with a tyre shrunk over a wheel centre having a crank and balance weight integral therewith, while the main axle and crankpin are forced or shrunk in. Such a case is examined with reference to a driving wheel of the London Midland and Scottish Railway locomotive Royal Scot, and the stress distributions measured in various parts of a model of it are described in detail.

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Internal stresses in the cross-grain direction in glulam induced by climate variations

Holzforschung ◽

10.1515/hf.2004.023 ◽

2004 ◽

Vol 58 (2) ◽

pp. 154-159 ◽

Cited By ~ 16

Author(s):

J. Jönsson

Keyword(s):

Climate Change ◽

Experimental Investigation ◽

Cross Section ◽

Moisture Gradient ◽

Internal Stresses ◽

Stress Distributions ◽

Climate Variations ◽

Before And After ◽

Stress States ◽

Natural Climate

Abstract Results are presented from an experimental investigation to determine internal stress states perpendicular to grain in glulam induced by moisture variations. The stresses are determined by measuring the released strains before and after cutting. Stress distributions are determined for specimens seasoned in constant humidity, specimens exposed to an artificial single climate change, specimens exposed to cyclic climate change and for specimens exposed to natural climate outdoors under shelter. Results for seasoned specimens show that internal stresses exist in glulam without the presence of moisture gradients. Stresses in specimens with an induced moisture gradient become larger when moistening from a specific climate A to another climate B than when drying from B to A. Tests in an outdoor sheltered climate show large variations in strains and stresses. The tensile stress level in the inner part of the glulam cross section exceeds the characteristic strength of 0.5 MPa during a period of approximately 80 days.

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