Preface

There are numerous factors that contribute to the deterioration of structures and infrastructures over time, including fatigue failure induced by traffic loads, the effects of environmental conditions, and natural catastrophes such as earthquakes. Continuous monitoring of the structure is needed to provide an early warning of a potentially dangerous state and an assessment of the structure's changes over time, rather than only routine or critical event-based inspections. Thus, structural health monitoring (SHM) has recently become a popular area of research in structural engineering. SHM is a field that has grown tremendously over the past few decades. This book brings together the most recent studies and state-of-the-art methodologies to improve understanding of how SHM can be applied in the real world, as well as how it can be improved, by highlighting its practical, theoretical, and historical applications. The book also examines challenges in SHM and sheds light on the future trends of SHM techniques for different types of response measurement and their applications in civil engineering structures and infrastructures.

> **Dr. Gobinath Ravindran** Department of Civil Engineering, SR University,

## **Dr. Vutukuru Mahesh**

Warangal, India

Department of Mechanical Engineering, SR University, Warangal, India

#### **Dr. Moustafa Moufid Kassem**

School of Civil Engineering, Universiti Sains Malaysia, Penang, Malaysia

**Chapter 1**

Parameter

**Abstract**

life, *ΔQL\**

**1**

**1. Introduction**

The Quantitative Estimation of

Mechanical Performance on the

Creep Fracture Life for Creep

*A. Toshimitsu Yokobori Jr and Go Ozeki*

Ductile Materials Based on *QL*\*

Previously, we have proposed creep deformation law estimated by non-dimensional time representation to predict creep fracture and remnant life. Furthermore, using steady state creep rate coupled with crack growth rate law based on *Q\** parameter, *QL\** parameter was derived and it was found to enable us to discriminate creep ductility and predict creep fracture life. In this study, a quantitative estimation and a prediction methods of mechanical performance on creep

strength (MPCS) and creep fracture life of the creep ductile materials including a weld joint notched specimen was noticed and the following studies were conducted. 1) The similarity law of creep deformation, 2) *QL\**map, which discriminates creep ductility and predicts creep fracture life, 3) Derivation method of mechanical indicators, "Converted stress", and *ΔQL\**, which quantify MPCS, 4) Example of the quantitative estimation by these parameters using P91 steel and its weld joint notched specimens. From these results, the concept of the converted stress and the *ΔQL\**were found to enable us to conduct quantitative estimation of MPCS and prediction of creep fracture life, with the short experimental period, the small number of specimens, the reasonable accuracy and an economic efficiency, which is an engineering significance.

**Keywords:** *QL\**, MPCS, converted stress, creep ductility, weld joint, creep fracture

Concerning the estimation of mechanical performance on creep and creep-fatigue interaction, the law on the relationship between applied stress and fracture life [1], the

Creep Strength and Prediction of
