Unable to generate references for document while using elsarticle class

Question

I have tried a lot to generate reference for my document using the elsarticle class for submission in Elsevier publications. But I don't know where I am making a mistake in getting the bibliography. Below I attach the code I used:

\documentclass[preprint,12pt]{elsarticle}
\usepackage{amssymb}
\journal{Nuclear Physics B}
\begin{document}
\begin{frontmatter}
\title{}
\author{}
\address{}
\begin{abstract}
\end{abstract}
\begin{keyword}
\end{keyword}
\end{frontmatter}
\section{Introduction}
\label{}
    Several researchers studied ruin probability, but for a survey
see\cite{conner2014making}. For bulk arrival queues see
\cite{frazier2014metal}
\section{\refname}
\bibliographystyle{elsarticle-num-names}
\bibliography{trialreferences}
\end{document}

and here is my bibliography file;

@article{conner2014making,
  title={Making sense of 3-D printing: Creating a map of additive manufacturing products and services},
  author={Conner, Brett P and Manogharan, Guha P and Martof, Ashley N and Rodomsky, Lauren M and Rodomsky, Caitlyn M and Jordan, Dakesha C and Limperos, James W},
  journal={Additive Manufacturing},
  volume={1},
  pages={64--76},
  year={2014},
  publisher={Elsevier}
}

@article{frazier2014metal,
    title={Metal additive manufacturing: a review},
    author={Frazier, William E},
    journal={Journal of Materials Engineering and Performance},
    volume={23},
    number={6},
    pages={1917--1928},
    year={2014},
    publisher={Springer}
}