Distortion failure occurs when a structure or component is deformed so that it can no longer support the load it was intended to carry. Every structure has a load limit beyond which it is considered unsafe or unreliable. Estimation of load limits is an important aspect of design and is commonly computed by classical design or limit analysis. This article discusses the common aspects of failure by distortion with suitable examples. Analysis of a distortion failure often must be thorough and rigorous to determine the root cause of failure and to specify proper corrective action. The article summarizes the general process of distortion failure analysis. It also discusses three types of distortion failures that provide useful insights into the problems of analyzing unusual mechanisms of distortion. These include elastic distortion, ratcheting, and inelastic cyclic buckling.

Dimensional and shape changes caused by heat treatment have been the subject of scientific and industrial research for a very long time. This article provides an overview of the complexity of distortion and stress generation during heat treatment of steels. It discusses the measurement and evaluation of dimensional and shape changes with examples. The article describes the mechanisms at work during the generation of stresses and distortion during heat treatment. A hypothetical experiment with increasing application to real life is used to develop a systematization of unavoidable size and shape changes. The article also provides information on the carriers of distortion potential that cause measureable size and shape changes.

The process of case hardening of steel includes three consecutive steps of heat treatment: heating; the thermochemical process with the enrichment of the surface area during the carburizing or carbonitriding stage with carbon and nitrogen; and the subsequent quenching process for hardening. This article provides a model-based description of the development of residual stresses during case hardening. It also describes the influence and effects of residual stresses and distortion in hardening, carburizing, and nitriding processes of the steel.

This article presents the three levels of investigations of distortion engineering. On Level 1, the parameters and variables influencing distortion in every manufacturing step must be identified. More than 200 parameters can affect distortion. The design of experiments approach allows for the investigation of larger numbers of parameters by a limited number of samples, and can be structured into system analysis, test strategy, test procedure, and test evaluation. Level 2 focuses on understanding the distortion mechanisms by using the concept of distortion potential and its carriers. Distortion engineering aims to compensate distortion using the so-called compensation potential (Level 3). Level 3 discusses the measures to improve homogeneity, and respectively the symmetry, of the carriers of the distortion potential. The article also discusses the compensation of the resulting size and shape changes of the existing asymmetries by well-directed insertions of additional inhomogeneity/asymmetries in one or more of the distributions of the carriers.

This article describes the fundamental concepts of heat treatment simulation, including the physical events and their interactions, the heat treatment simulation software, and the commonly used simulation strategies. It summarizes material data needed for heat treatment simulations and discusses reliable data sources as well as experimental and computational methods for material data acquisition. The article provides information on the process data needed for accurate heat treatment simulation and the methods for their determination. Methods for validating heat treatment simulations are also discussed with an emphasis on the underlying philosophy for the selection and design of validation tests. The article also discusses the applications, capabilities, and limitations of heat treatment simulations via selected industrial case studies for a better understanding of the effect of microstructure, distortion, residual stress, and cracking in gears, shafts, and bearing rings.

In the case of steels, heat treatment plays a fundamental role because no other process step can manipulate the microstructure in order to fulfill such a wide variety of possible in-service conditions. This article addresses heat treatment with regard to hardening and subsequent tempering of steel components in order to optimize tribological properties. It focuses on the heat treatment of tempering and bearing steels and on volume changes that take place due to phase transformations. Plastic deformations that occur due to shrinking and phase transformation are also discussed. The article also describes the generation of thermal, transformation, and hardening residual stresses.

This article summarizes some issues and approaches in performing computational analyses of mechanical behavior, distortion, and hot tearing during solidification. It presents the governing equations and describes the methods used to solve them. The article reviews the finite element formulation, multidomain approaches, and arbitrary Lagrangian Eulerian method in solidification modeling. It illustrates the sand casting of braking disks and continuous casting of steel slabs.

This article discusses distortion due to differences in solidification times and its two solutions. The solutions include compensating the distortion in a pattern in the direction opposite to that of the observed distortion and increasing the section thickness of an end member and subsequently machining the section to the desired size. The distortion due to mold restraint and its elimination by redesigning or by adding tie bars are described. The article reviews the distortion that occurs in heat treating and its solution. It concludes with a discussion on the influence of alloy to be cast on distortion.

This article describes the formation of residual stresses and distortion and the techniques for measuring residual stresses. It provides a discussion on the magnitude and distribution analysis of residual stresses and distortion in weldments. The article considers the effects of residual stresses and distortion on the brittle fracture and fatigue fracture of welded structures. The thermal treatments of weldments are also discussed.

The design of a tool-steel part directly affects the susceptibility to shape distortion on heating and cooling. This article provides information on the selection of chemical composition and the effect of composition on size distortion. It explains the various factors considered to control distortion in tools steels, namely, design, initial condition, machining procedure, and heat treatment. Distortion can occur both during and after heat treatment. The article discusses the chief ways to precisely control the extent of distortion by heat treating and auxiliary mechanical methods. Stabilizing treatments, namely, stabilizing by tempering and stabilizing by cold treatment are used to minimize dimensional changes that occur following heat treatment.

Distortion, encompassing all irreversible dimensional changes, is of two main types: size distortion and shape distortion. This article provides an overview of the nature and causes of distortion and discusses the process and material aspects of distortion specific to steels and tool steels. It also discusses the prediction of distortion and residual stresses by heat treatment simulation for optimizing production processes. The advantages and limitations of heat treatment simulation are also described.

This article provides a discussion on the analytical modeling and simulation of residual stress states developed in steel parts and the reasons for these varied final stress states. It illustrates how the metallurgical phase transformation of steel alloys can be applied in the simulation of induction hardening processes and the role of these phase transformations in affecting stress and distortion. Emphasis is placed on induction surface hardening, which is the main application of induction heating in steel heat treatment. The article concludes with examples of induction surface-hardened shafts and through-hardened shafts made of plain carbon steel, alloy steel, and limited hardenability steel.

This article describes the formation of residual stresses and distortion, providing information on the techniques for measuring residual stresses. It presents a detailed discussion on the magnitude and distribution analysis of the residual stresses and distortion in weldments. The article briefly explains the effects of residual stresses and distortion on the brittle fracture and fatigue fracture of welded structures. It also provides information on the thermal treatments of weldments.

Distortion often is observed in the analysis of other types of failures, and consideration of the distortion can be an important part of the analysis. This article first considers that true distortion occurs when it was unexpected and in which the distortion is associated with a functional failure. Then, a more general consideration of distortion in failure analysis is introduced. Several common aspects of failure by distortion are discussed and suitable examples of distortion failures are presented for illustration. The article provides information on methods to compute load limits, errors in the specification of the material, and faulty process and their corrective measures to meet specifications. It discusses the general process of material failure analysis and special types of distortion and deformation failure.

Modeling will help reduce machining problems and thereby enable more rapid introduction of high-performance materials and components. This article discusses the technical needs of aircraft engine and airframe structural components and modeling of heat-treat-induced residual stress by finite-element residual-stress analysis. It describes the two-dimensional (2-D) and three-dimensional (3-D) procedures involved in finite-element residual-stress analysis. The article deals with the 2-D and 3-D machining distortion validation on engine-disk-type components. It describes methods for obtaining machining-induced residual stresses, including detailed finite-element analysis of the cutting process, the simple fast-acting mechanistic model, and the semi-empirical linear stress model. The article concludes with information on the modeling benefits and implementation of modeling in a production environment.

This article provides the basics of overall quench process distortion. It describes the influence of quenching processes on the generation of distortion. Examples for the distortion behavior of different types of components are presented. Then, comparisons between different quenching processes are provided. The article presents some possibilities for minimization of shape changes by the quenching process itself. Several suggestions are given for quenching processes in evaporating fluids. An example is provided for out-of-roundness reduction for rings by well-defined inhomogeneous quenching in a gas nozzle field. Another example shows how intensive and high-speed quenching can help to reduce the bending of shafts with an asymmetrical cross-section. The last example shows the result when external loads and nonsymmetric quenching act together. The article also presents test samples for the judgment about distortion potential arising from heat treatment equipment.